Riboflavin Binding Protein (RBP) is synthesized in the liver and oviduct of a laying hen and transports Riboflavin to the egg where it later sustains the development of the chick. A mutant chicken strain, incapable of synthesizing RBP, lays eggs which are unable to hatch unless rescued by injection of the vitamin into the egg. Adult chickens with the disease suffer no apparent effects, suggesting the protein is required only for oogenesis. Homologous proteins have been partially characterized in rats and humans and the human homologue has been partially purified from human placental and umbilical cord tissue. Avian RBP has been extensively characterized as a stable glycophosphoprotein. The cDNA for RBP has been cloned as have a number of the introns in the 5' region of the gene. Of particular interest is the mechanism by which estrogen stimulates transcription of the RBP message. We propose to sequence the gene promoter region of chicken RBP, and characterize aspects of gene regulation. This project would be invaluable in that 1) characterization of the promoter for RBP would indicate the elements responsible for steroid responsiveness, 2) cloning of the promoter and remaining intronic sequences would allow us to establish the mechanisms by which tissue specific gene expression are conferred. Of particular interest would be the elucidation of the elements responsible for oviducal specificity. Further characterization of this gene would serve as a model for understanding the regulation of the vitamin transport process in humans, especially those involved in fetal growth and development.